Fifty-five people have contracted drug-resistant Campylobacter infections in a multistate outbreak linked to pet store puppies, according to a CDC update posted Tuesday.

The new total marks a 16-case increase since the CDC's Sept. 11 update. Thirteen individuals have required hospitalization. The outbreak, which began Sept. 15, 2016, stems from infected puppies at Petland pet stores across multiple states.

Campylobacteriosis is an infectious disease caused by Campylobacter bacteria. The bacteria can be contracted through contact with contaminated feces and is not usually spread via person-to-person contact. Most sickened individuals experience diarrhea, cramping, abdominal pain and fever two days to five days after bacterial exposure. The diarrhea may be bloody. The illness typically lasts about a week.